The present invention relates to an image signal processing apparatus, and more particularly to a motion-adaptive type luminance (Y) and chrominance (C) signal separator which can improve picture quality by separating luminance and chrominance signals based on vertical and horizontal motion components which arise during the separation of luminance (Y) and chrominance (C) signals from composite image signals.
Conventionally, in order to process luminance and chrominance signals, first they were separated from composite image signals, and then were separated using a comb filter.
However, in using a comb filter to separate Y and C signals, picture quality was degraded because of failure to consider the issue of correlation between motion components of the signals. As a result, the conventional method was unable to prevent various interference phenomena such as those caused by a so-called hanging dot and its motion.
A hanging dot arises from the following situation. FIGS. 1A and 1B represent a portion of a color carrier signal before and after processing through a comb filter, respectively. In FIG. 1A, the central part of the color carrier signal portion has both a luminance and a chrominance signal component, whereas the outer part has only a luminance signal component. There is a boundary between the two. In FIG. 1B, after being passed through a comb filter, the boundary has dotted portions on at least two sides. Those dotted boundary parts are caused by a hanging dot, which can move along that boundary part to provide the dotted effect shown in FIG. 1B.
In view of this problem, it would be desirable to consider effects of motion components of the signals during separation, thus taking into account the need for correlation.